Jeroen J. Lammerts van Bueren

Human IgG2 Antibodies against Epidermal Growth Factor Receptor Effectively Trigger Antibody-Dependent Cellular Cytotoxicity but, in Contrast to IgG1, Only by Cells of Myeloid Lineage

Ab-dependent cellular cytotoxicity (ADCC) is usually considered an important mechanism of action for immunotherapy with human IgG1 but not IgG2 Abs. The epidermal growth factor receptor (EGF-R) Ab panitumumab represents the only human IgG2 Ab approved for immunotherapy and inhibition of EGF-R signaling has been described as its principal mechanism of action. In this study, we investigated effector mechanisms of panitumumab compared with zalutumumab, an EGF-R Ab of the human IgG1 isotype. Notably, panitumumab was as effective as zalutumumab in recruiting ADCC by myeloid effector cells (i.e., neutrophils and monocytes) in contrast to NK cell-mediated ADCC, which was only induced by the IgG1 Ab. Neutrophil-mediated tumor cell killing could be stimulated by myeloid growth factors and was triggered via FcγRIIa. Panitumumab-mediated ADCC was significantly affected by the functional FcγRIIa-R131H polymorphism and was induced more effectively by neutrophils from FcγRIIa-131H homozygous donors than from -131R individuals. This polymorphism did not affect neutrophil ADCC induced by the IgG1 Ab zalutumumab. The in vivo activity of both Abs was assessed in two animal models: a high-dose model, in which signaling inhibition is a dominant mechanism of action, and a low-dose model, in which effector cell recruitment plays a prominent role. Zalutumumab was more effective than panitumumab in the high-dose model, reflecting its stronger ability to induce EGF-R downmodulation and growth inhibition. In the low-dose model, zalutumumab and panitumumab similarly prevented tumor growth. Thus, our results identify myeloid cell-mediated ADCC as a potent and additional mechanism of action for EGF-R–directed immunotherapy.

Dual Mode of Action of a Human Anti-Epidermal Growth Factor Receptor Monoclonal Antibody for Cancer Therapy

Epidermal growth factor receptor (EGF-R) overexpression is common in a large number of solid tumors and represents a negative prognostic indicator. Overexpression of EGF-R is strongly tumor associated, and this tyrosine kinase type receptor is considered an attractive target for Ab therapy. In this study, we describe the evaluation of mAb 2F8, a high avidity human mAb (IgG1κ) directed against EGF-R, developed using human Ig transgenic mice. mAb 2F8 effectively blocked binding of EGF and TGF-α to the EGF-R. At saturating concentrations, 2F8 completely blocked EGF-R signaling and inhibited the in vitro proliferation of EGF-R-overexpressing A431 cells. At much lower concentrations, associated with low receptor occupancy, 2F8 induced efficient Ab-dependent cell-mediated cytotoxicity (ADCC) in vitro. In vivo studies showed potent antitumor effects in models with A431 tumor xenografts in athymic mice. Ex vivo analysis of the EGF-R status in tumor xenografts in 2F8-treated mice revealed that there are two therapeutic mechanisms. First, blocking of EGF-R signaling, which is most effective at complete receptor saturation and therefore requires a relatively high Ab dose. Second, at very low 2F8 receptor occupancy, we observed potent antitumor effects in mice, which are likely based on the engagement of immune effector mechanisms, in particular ADCC. Taken together, our findings indicate that ADCC represents an important effector mechanism of this Ab, which is effective at relatively low dose.

Antibody-mediated phagocytosis contributes to the anti-tumor activity of the therapeutic antibody daratumumab in lymphoma and multiple myeloma

Daratumumab (DARA) is a human CD38-specific IgG1 antibody that is in clinical development for the treatment of multiple myeloma (MM). The potential for IgG1 antibodies to induce macrophage-mediated phagocytosis, in combination with the known presence of macrophages in the tumor microenvironment in MM and other hematological tumors, led us to investigate the contribution of antibody-dependent, macrophage-mediated phagocytosis to DARAs mechanism of action. Live cell imaging revealed that DARA efficiently induced macrophage-mediated phagocytosis, in which individual macrophages rapidly and sequentially engulfed multiple tumor cells. DARA-dependent phagocytosis by mouse and human macrophages was also observed in an in vitro flow cytometry assay, using a range of MM and Burkitts lymphoma cell lines. Phagocytosis contributed to DARAs anti-tumor activity in vivo, in both a subcutaneous and an intravenous leukemic xenograft mouse model. Finally, DARA was shown to induce macrophage-mediated phagocytosis of MM cells isolated from 11 of 12 MM patients that showed variable levels of CD38 expression. In summary, we demonstrate that phagocytosis is a fast, potent and clinically relevant mechanism of action that may contribute to the therapeutic activity of DARA in multiple myeloma and potentially other hematological tumors.

Effect of Target Dynamics on Pharmacokinetics of a Novel Therapeutic Antibody against the Epidermal Growth Factor Receptor: Implications for the Mechanisms of Action

The epidermal growth factor receptor (EGFR) is overexpressed on many solid tumors and represents an attractive target for antibody therapy. Here, we describe the effect of receptor-mediated antibody internalization on the pharmacokinetics and dose-effect relationship of a therapeutic monoclonal antibody (mAb) against EGFR (2F8). This mAb was previously found therapeutically active in mouse tumor models by two dose-dependent mechanisms of action: blockade of ligand binding and induction of antibody-dependent cell-mediated cytotoxicity. In vitro studies showed 2F8 to be rapidly internalized by EGFR-overexpressing cells. In vivo, accelerated 2F8 clearance was observed in cynomolgus monkeys at low doses but not at high doses. This enhanced clearance seemed to be receptor dependent and was included in a pharmacokinetic model designed to explain its nonlinearity. Receptor-mediated clearance was also found to affect in situ antibody concentrations in tumor tissue. Ex vivo analyses of xenograft tumors of 2F8-treated nude mice revealed that relatively high antibody plasma concentrations were required for maximum EGFR saturation in high-EGFR-expressing human A431 tumors, in contrast to lower-EGFR-expressing human xenograft tumors. In summary, receptor-mediated antibody internalization and degradation provides a saturable route of clearance that significantly affects pharmacokinetics, particularly at low antibody doses. EGFR saturation in normal tissues does not predict saturation in tumor tissue as local antibody concentrations in EGFR-overexpressing tumors may be more rapidly reduced by antibody internalization. Consequently, antibody saturation of the receptor may be affected, thereby affecting the local mechanism of action.

Anti-galactose-α-1,3-galactose IgE from allergic patients does not bind α-galactosylated glycans on intact therapeutic antibody Fc domains

Anti-galactose-α-1,3-galactose IgE from allergic patients does not bind α-galactosylated glycans on intact therapeutic antibody Fc domains

Monoclonal antibodies targeting CD38 in hematological malignancies and beyond

CD38 is a multifunctional cell surface protein that has receptor as well as enzyme functions. The protein is generally expressed at low levels on various hematological and solid tissues, while plasma cells express particularly high levels of CD38. The protein is also expressed in a subset of hematological tumors, and shows especially broad and high expression levels in plasma cell tumors such as multiple myeloma (MM). Together, this triggered the development of various therapeutic CD38 antibodies, including daratumumab, isatuximab, and MOR202. Daratumumab binds a unique CD38 epitope and showed strong anti‐tumor activity in preclinical models. The antibody engages diverse mechanisms of action, including complement‐dependent cytotoxicity, antibody‐dependent cellular cytotoxicity, antibody‐dependent cellular phagocytosis, programmed cell death, modulation of enzymatic activity, and immunomodulatory activity. CD38‐targeting antibodies have a favorable toxicity profile in patients, and early clinical data show a marked activity in MM, while studies in other hematological malignancies are ongoing. Daratumumab has single agent activity and a limited toxicity profile, allowing favorable combination therapies with existing as well as emerging therapies, which are currently evaluated in the clinic. Finally, CD38 antibodies may have a role in the treatment of diseases beyond hematological malignancies, including solid tumors and antibody‐mediated autoimmune diseases.

Novel human antibody therapeutics: The age of the Umabs

Monoclonal antibodies represent a major and increasingly important category of biotechnology products for the treatment of human diseases. The state‐of‐the‐art of antibody technology has evolved to the point where therapeutic monoclonal antibodies, that are practically indistinguishable from antibodies induced in humans, are routinely generated. We depict how our science‐based approach can be used to further improve the efficacy of antibody therapeutics, illustrated by the development of three monoclonal antibodies for various cancer indications: zanolimumab (directed against CD4), ofatumumab (directed against CD20) and zalutumumab (directed against epidermal growth factor receptor).

When blood transfusion medicine becomes complicated due to interference by monoclonal antibody therapy

Monoclonal antibodies (MoAbs) are increasingly integrated in the standard of care. The notion that therapeutic MoAbs can interfere with clinical laboratory tests is an emerging concern that requires immediate recognition and the development of appropriate solutions. Here, we describe that treatment of multiple myeloma patients with daratumumab, a novel anti‐CD38 MoAb, resulted in false‐positive indirect antiglobulin tests (IATs) for all patients for 2 to 6 months after infusion. This precluded the correct identification of irregular blood group antibodies for patients requiring blood transfusion.

The Therapeutic CD38 Monoclonal Antibody Daratumumab Induces Programmed Cell Death via Fcγ Receptor–Mediated Cross-Linking

Emerging evidence suggests that FcγR-mediated cross-linking of tumor-bound mAbs may induce signaling in tumor cells that contributes to their therapeutic activity. In this study, we show that daratumumab (DARA), a therapeutic human CD38 mAb with a broad-spectrum killing activity, is able to induce programmed cell death (PCD) of CD38+ multiple myeloma tumor cell lines when cross-linked in vitro by secondary Abs or via an FcγR. By comparing DARA efficacy in a syngeneic in vivo tumor model using FcRγ-chain knockout or NOTAM mice carrying a signaling-inactive FcRγ-chain, we found that the inhibitory FcγRIIb as well as activating FcγRs induce DARA cross-linking–mediated PCD. In conclusion, our in vitro and in vivo data show that FcγR-mediated cross-linking of DARA induces PCD of CD38-expressing multiple myeloma tumor cells, which potentially contributes to the depth of response observed in DARA-treated patients and the drug’s multifaceted mechanisms of action.

Epidermal Growth Factor Receptor (EGFR) Antibody-Induced Antibody-Dependent Cellular Cytotoxicity Plays a Prominent Role in Inhibiting Tumorigenesis, Even of Tumor Cells Insensitive to EGFR Signaling Inhibition

Ab-dependent cellular cytotoxicity (ADCC) is recognized as a prominent cytotoxic mechanism for therapeutic mAbs in vitro. However, the contribution of ADCC to in vivo efficacy, particularly for treatment of solid tumors, is still poorly understood. For zalutumumab, a therapeutic epidermal growth factor receptor (EGFR)-specific mAb currently in clinical development, previous studies have indicated signaling inhibition and ADCC induction as important therapeutic mechanisms of action. To investigate the in vivo role of ADCC, a panel of EGFR-specific mAbs lacking specific functionalities was generated. By comparing zalutumumab with mAb 018, an EGFR-specific mAb that induced ADCC with similar potency, but did not inhibit signaling, we observed that ADCC alone was insufficient for efficacy against established A431 xenografts. Interestingly, however, both zalutumumab and mAb 018 prevented tumor formation upon early treatment in this model. Zalutumumab and mAb 018 also completely prevented outgrowth of lung metastases, in A431 and MDA-MB-231-luc-D3H2LN experimental metastasis models, already when given at nonsaturating doses. Finally, tumor growth of mutant KRAS-expressing A431 tumor cells, which were resistant to EGFR signaling inhibition, was completely prevented by early treatment with zalutumumab and mAb 018, whereas ADCC-crippled N297Q-mutated variants of both mAbs did not show any inhibitory effects. In conclusion, ADCC induction by EGFR-specific mAbs represents an important mechanism of action in preventing tumor outgrowth or metastasis in vivo, even of cancers insensitive to EGFR signaling inhibition.